Driver board control system for modular conveyor with address-based network for inter-conveyer communication

ABSTRACT

A method and control system are provided for controlling a modular conveyor system, which may be networked together with other such systems in order to implement a control strategy for a modular conveyor system. The control system comprises a communications port for interconnection of the control system with a network for sending outgoing addressed data to other devices on the address-based network and for receiving incoming addressed data from other devices. The control system further comprises a logic system, which may receive a signal from an object sensor and provide a control signal or output adapted to control activation of a motorized roller assembly, based on an input signal from the object sensor or the communications port. The logic system may provide for single step operation whereby system troubleshooting may be facilitated, and in addition may provide situation aware and output value source selection functionality.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 10/309,400, filed on Dec. 3, 2002, entitled DRIVER BOARDCONTROL SYSTEM FOR MODULAR CONVEYOR WITH ADDRESS-BASED NETWORK FORINTER-CONVEYER COMMUNICATION, which is a continuation of U.S. patentapplication Ser. No. 09/729,486 filed on Dec. 4, 2000, entitled DRIVERBOARD CONTROL SYSTEM FOR MODULAR CONVEYOR WITH ADDRESS-BASED NETWORK FORINTER-CONVEYOR COMMUNICATION, which is a continuation-in-part ofco-pending U.S. patent application Ser. No. 09/559,625 filed Apr. 27,2000; Ser. No. 09/574,982 filed May 19, 2000; Ser. No. 09/644,635 filedAug. 23, 2000; and Ser. No. 09/669,822 filed Sep. 26, 2000, theentireties of all such applications of which are incorporated herein byreference.

TECHNICAL FIELD

[0002] The present invention relates to the art of industrialcontrollers, and more particularly to systems and methods forcontrolling a modular conveyor.

BACKGROUND OF THE INVENTION

[0003] Industrial controllers are special purpose computers used forcontrolling industrial processes, manufacturing equipment, and otherfactory automation, such as conveyor systems. In accordance with acontrol program, the industrial controller measures one or more processvariable or inputs reflecting the status of a controlled conveyorsystem, and changes outputs effecting control of the conveyor system.The inputs and outputs may be binary, (e.g., on or off), as well asanalog inputs and outputs assuming a continuous range of values. Thecontrol program may be executed in a series of execution cycles withbatch processing capabilities.

[0004] The measured inputs received from a conveyor system and theoutputs transmitted to the conveyor system generally pass through one ormore input/output (I/O) modules. These I/O modules serve as anelectrical interface between the controller and the conveyor system, andmay be located proximate or remote from the controller. The inputs andoutputs may be recorded in an I/O table in processor memory. Inputvalues may be asynchronously read from the controlled conveyor system byone or more input modules and output values are written directly to theI/O table by the processor for subsequent communication to the conveyorsystem by specialized communications circuitry. An output module mayinterface directly with a conveyor system, by providing an output froman I/O table to an actuator such as a motor, valve, solenoid, and thelike.

[0005] During execution of the control program, values of the inputs andoutputs exchanged with the conveyor system may pass through the I/Otable. The values of inputs in the I/O table are asynchronously updatedfrom the controlled conveyor system by dedicated scanning circuitry.This scanning circuitry may communicate with input modules over a bus ona backplane or network communications. The scanning circuitry alsoasynchronously writes values of the outputs in the I/O table to thecontrolled conveyor system. The output values from the I/O table arethen communicated to one or more output modules for interfacing theconveyor system. Thus, the processor may simply access the I/O tablerather than needing to communicate directly with the conveyor system.

[0006] An industrial controller may be customized to the particularprocess by writing control software that may be stored in thecontroller's memory and/or by changing the hardware configuration of thecontroller to match the control task. Controller hardware configurationis facilitated by separating the industrial controller into a number ofcontrol modules, each of which is performing a different function.Particular control modules needed for the control task may then beconnected together on a common backplane within a rack. The controlmodules may include processors, power supplies, network communicationmodules, and I/O modules exchanging input and output signals directlywith the controlled conveyor system. Data may be exchanged betweenmodules using a backplane communications bus, which may be serial orparallel. A typical hardware modification may involve adding additionalI/O modules in order to be able to control additional equipment.

[0007] Various control modules of the industrial controller may bespatially distributed along a common communication link in severalracks. Certain I/O modules may thus be located in close proximity to aportion of the control equipment, and away from the remainder of thecontroller. Data is communicated with these remote modules over a commoncommunication link, or network, wherein all modules on the networkcommunicate using a standard communications protocol.

[0008] In a typical distributed control system, one or more outputmodules are provided for interfacing with a process. The outputs derivetheir control or output values in the form of a message from a master orpeer device over a network or a backplane. For example, an output modulemay receive an output value from a processor, such as a programmablelogic controller (PLC), via a communications network or a backplanecommunications bus. The desired output value is generally sent to theoutput module in a message, such as an explicit message or an I/Omessage. The output module receiving such a message will provide acorresponding output (analog or digital) to the controlled process.

[0009] Control systems are often employed in association with conveyorsystems for moving objects along guided tracks, including modularconveyor sections or “sticks”. Conveyor systems for moving objectsbetween stations in a manufacturing environment or for accumulating anddistributing products in a warehouse operation are well known in theart. Such conveyor systems provide upwardly exposed conveying surfaces,such as rollers, positioned between guiding side rails. The rollers arepowered by controllable motors to move objects placed on top of themalong a track defined by the rails.

[0010] Assembly of conveyor systems is facilitated by the use of“conveyor sticks” which may include one or more short sections ofrollers and guide rails, which are connected together to form the finalconveyor system. The conveying surface of each conveyor stick may bebroken up into one or more zones, each associated with a sensor fordetecting the presence of an object on the conveyor at the zone. Acontrol circuit communicates with each zone and sensor via a number ofcables to control the zones, in order to accomplish a number ofstandardized tasks.

[0011] Such conveyor systems may be adapted to perform one or more tasksor operations. One such task is that of “accumulation” in which acontrol circuit for a given zone operates its rollers when the sensor,in an upstream zone, indicates an object is at that zone and the sensorof a “downstream” zone indicates that no object is in that downstreamzone. This logic causes the conveyor zones to move objects along to fillall zones with objects. In a “slug release” operation, each controlcircuit in a defined release zone operates its rollers if its sensorindicates an object is present and no object is in the downstream zonefrom the defined release zone. This logic causes the emptying of apredefined section of the conveyor, typically to a downstream portion. Athird mode of operation is “singulation release” in which a singleobject at a time is unloaded from the conveyor system. Each upstreamcontrol circuit operates its rollers to move its objects downstream onezone.

[0012] In order to perform these tasks, the control circuit for aparticular conveyor stick may communicate in a limited fashion with thecontrol circuits (or at least the sensors) of associated upstream anddownstream conveyor sticks. This may be accomplished via cabling betweencontrol cards or sensors of the conveyor sticks, typically within one ofthe side rails. The conveyor system may operate without the need for acentral controller, for example, such as where one or more I/O pointsare provided for each zone, thus reducing the wiring associatedtherewith. By eliminating the need for such wiring, the conveyor stickscan be easily assembled or reconfigured. Nevertheless, the lack ofcentral control makes the conveyor system relatively hard to reconfigurerequiring, for example, settings to being manually adjusted on eachcontroller board when delay times and conveyor speeds are changed.Further, lack of centralized communication between components of theconveyor system makes it difficult to detect and report conveyor systemproblems such as motor failure or material jamming.

[0013] Some conventional control devices and systems for such conveyorsystems provide outputs solely based on messages from a network, havingno internal logic. For example, such a device may provide an outputaccording to an output value received in an I/O message from a master(e.g., a PLC), and may maintain that value during normal operation untilanother message is received. In some such devices, certain conditionscan affect the output value. For instance, when a module detects acommunications fault, the output may go to a known state. However, thereare many sources that may affect an output point's value. These includean I/O message, an explicit message, local logic, fault or idle values,and/or a forcing message. Heretofore, the source of an output value wasdetermined according to fixed controller architecture constraints. Thus,a user had limited ability to decide priorities for the source of aconveyor system output module's output value. In addition, there aremany conditions or events associated with conveyor systems for which itmay be desirable to provide another output value to the device.Heretofore, a user had no ability or a limited ability to define outputdevice behavior in lieu of regular I/O messages.

[0014] In addition, some conventional conveyor control devices provide arun mode wherein a module executes a control program and a configuremode wherein the control program execution is suspended. As conveyorcontrol systems become more widely distributed, the logic or controlprogram associated with a particular system may be executed on a largenumber of modules or devices. In this way, individual processors in thedevices execute a program autonomously from the rest of the systemcomponents. Smart devices, such as I/O modules, transducers, sensors,valves, and the like may thus be programmed to execute certain logicalor other programs or operations independently from other such devices.

[0015] The distribution of smart devices in a networked conveyor controlsystem has many advantages. However, system testing and troubleshootingare often more difficult in distributed systems. In a system with manyautonomous smart devices, each having its own control logic or program,problems in system performance cannot easily be traced to a specificdevice. Once the component devices in such a system are placed intoexecute or run mode, the logic or control programs associated therewithrun independently, and are often not synchronized. Even where certainconveyor control devices in a system are synchronized to certain events,determining the source of a system control problem is still difficult.

[0016] In many cases, the source of a control problem is an error inprogramming a particular module. For example, the logic function in aparticular module may be the function of several input values or states.Problems in the logic function may only be discernable in one or a smallnumber of input combinations. In widely distributed conveyor controlsystem architectures, system events occur asynchronously, such as I/Ovalue state changes, messages, etc. Thus, when a problem occurs, it maybe difficult to determine the source of the error.

[0017] This is particularly problematic in system startup situations.Large conveyor control systems are typically tested before applicationto a real process, with inputs simulated and outputs tested under avariety of input conditions. In addition, control system diagnostics areneeded in the field, when problems in system performance are recognized,or when system parameters are changed. Present diagnostic tools aretypically limited to simulating input signals and monitoring outputvalues. Conventional control devices do not provide for ease oftroubleshooting in such distributed conveyor control systemapplications.

SUMMARY OF THE INVENTION

[0018] The following presents a simplified summary of the invention inorder to provide a basic understanding of some aspects of the invention.This summary is not an extensive overview of the invention. It isintended to neither identify key or critical elements of the inventionnor delineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

[0019] The present invention provides a conveyor control system, whichmay be networked together with other such systems in order to implementa control strategy for a modular conveyor system. An address-basednetwork connects control components within conveyor sticks togetherallowing control, monitoring or configuration of the components withinthe conveyor sticks from a central device. The control system accordingto the invention may further be adapted to perform self-configuration,whereby individual control systems may configure themselves on power upin order to communicate with one or more adjacent or related controlsystems, in order to effectuate a control strategy for the conveyorsystem. The conveyor control system may also be employed in non-modularor continuous conveyor systems in accordance with the invention.

[0020] The conveyor sections may comprise separated upstream anddownstream ends having mechanical connectors for connecting todownstream and upstream ends, respectively, of other conveyor sections.The conveyor sections support motorized roller assemblies and associatedobject sensors sensing objects on the conveyor section. A communicationsport in the individual control systems provides for interconnection ofthe control system with the address-based network for sending outgoingaddressed data to other devices on the address-based network and forreceiving incoming addressed data from other devices. Moreover, thecontrol system communications ports may provide for sending andreceiving broadcast messages as well as individually addressed messages,for example, wherein a control system may send a universal broadcastmessage to all devices on the network.

[0021] The control system further comprises a logic system communicatingwith or being part of the communications port, which may receive asignal from an object sensor and provide a control signal or outputadapted to control activation of a motorized roller assembly, based onan input signal from the object sensor or the communications port. Forexample, an external object presence signal associated with at least oneof the other conveyor sections or another component within a conveyorsection may be received by the communications port from theaddress-based network. The invention further contemplates controlsystems having a logic system, where the control system provides asensor functionality, whereby the presence of an object is sensed, and asignal or message is provided to the address-based network. Accordingly,the logic system may further transmit an object presence signal asoutgoing addressed (e.g., or broadcast) data through the communicationsport, independent of whether an output or control signal is provided bythe control system. The logic system may be further adapted to performsituation-aware configuration and execution functions and output valuesource selection functions in order to reduce or minimize theabove-mentioned shortcomings in conventional conveyor controls, and/ormay support single-stepped or strobed synchronization to facilitateconveyor system setup and diagnostics. It will be appreciated that thestrobed synchronization or single-step mode of operating the controlsystem may be employed in addition to communications protocols wherein amaster device sends a strobe or broadcast message to a plurality ofslave devices on a network, to which slaves may then respond one afteranother according to their individual network address settings, which issometimes referred to as strobed communications. In this regard, themethods and systems of the present invention find application inassociation with numerous communications protocols, including polledcommunications, strobed or broadcast communications, and others, and itwill be understood that such communications protocols fall within thescope of the present invention. The logic system, moreover, may compriseseparate program attributes for different drive roller products made bydifferent vendors.

[0022] In accordance with one aspect of the invention, there is provideda control system for a modular conveyor, such as a conveyor having amotorized roller for moving objects on the modular conveyor and anobject sensor for sensing objects on the modular conveyor. The controlsystem comprises a drive controller adapted to control a motorizedroller in the modular conveyor, a communications port adapted to connectthe control system to an address-based network, to send outgoingaddressed data to other devices in the address-based network, and toreceive incoming addressed data from the address-based network. Thecontrol system further comprises a logic system adapted to receive aninput signal from either the object sensor or the communications port orboth, and to provide a roller control signal to the motorized rolleraccording to the input signal.

[0023] In accordance with another aspect of the invention, the logicsystem may comprise an output module, which includes a value sourceselector adapted to receive messages from the address-based network, anda local logic function associated with the value source selector tocreate a binding and providing a signal thereto. The logic function mayfurther include an output receiving an output value from the valuesource selector based on the signal from the local logic function, andhaving an output signal. The value source selector may be adapted toselectively ignore I/O and explicit messages from the address-basednetwork based on the binding and to selectively use an idle action andset the output value according to an idle value when the local logicfunction is disabled. In addition, the value source selector mayselectively use a fault action and set the output value according to afault value based on an override attribute, and selectively ignore idlemessages according to the override attribute.

[0024] According to yet another aspect of the present invention, thelogic system may comprise an output providing an output signal accordingto an output value, an indicator adapted to receive message informationfrom the communications port and providing indicator data, and a logicunit, which receives message information from the communications portand indicator data from the indicator. The logic unit is adapted toperform a logic function, and to selectively provide the output value tothe output according to the message information or the logic function.

[0025] The logic unit may thus take into account indicator data indetermining the output value, which was possible in previous conveyorcontrollers. For example, the indicator data may include an I/Oconnection health indicator, a messaging connection health indicator, anI/O connection error indicator, a run event indicator, and idle eventindicator, a network error indicator, an I/O point fault indicator, ahardware input indicator, a hardware output indicator, and I/O data. Thecontrol system thus allows a user to define both the status/eventindicators which will be considered, as well as the decisional logicused in providing an output value to the output of the device. The logicunit, for example, may comprise a processor or other logic device, whichmay be configured by a user to perform various functions, such asboolean operations, flip-flops, counters, and/or timers.

[0026] In accordance with still another aspect of the invention, a usermay place one or more conveyor control systems or devices into a stepmode, wherein the control systems are adapted to execute a specifiednumber of iterations of their internal logic or control programs, orexecute such programs for a specified time period, and then stop orsuspend execution. The user may then perform system diagnostics, forexample, by interrogating certain conveyor section controllers to obtainstatus information, output and input values, and the like. The systemmay then be further iterated and the process repeated, in order toenable the identification of logic programming and/or hardware problemsin a system. In this regard, the logic system may be adapted to executea stored program and to receive a message from a master device via thecommunications port, wherein the message comprises a parameter. Thelogic system is further adapted to execute at least a portion of thestored program according to the parameter and to subsequently suspendexecution of the stored program according to the parameter. Theinvention thereby provides significantly improved diagnostic andtroubleshooting capabilities over conventional conveyor control systemsand devices.

[0027] According to another aspect of the invention, a method isprovided for controlling a modular conveyor system. The method may beimplemented, for example, in a modular conveyor control system having adrive controller adapted to control a motorized roller as well as acommunications port adapted to connect the control system to anaddress-based network. The method comprises providing a logic system inthe control system, receiving an input signal from an object sensorassociated with the modular conveyor or from the communications port,and providing a roller control signal to the motorized roller accordingto the input signal.

[0028] According to yet another aspect of the invention, the logicsystem comprises an output device adapted to provide an output accordingto an output value, wherein the method may further comprise associatingthe output device with a logic function, providing the output valueaccording to the logic function, and ignoring explicit messages from theaddress-based network. In this regard, the method may further includeignoring value messages from the address-based network, selectivelyignoring fault messages according to an override attribute, andselectively ignoring idle messages according to the override attribute.

[0029] According to another aspect of the invention, the logic systemmay comprise an output device having a device status, wherein the methodfurther comprises associating the output device with a logic function incommunication with the address-based network, and associating the logicfunction with an indicator. In addition, the method may includereceiving a status message from the address-based network, receiving avalue message from the address-based network, updating the indicatoraccording to the status message and the device status, and selectivelyproviding an output value to the output device from one of the logicfunction and the value message, according to the logic function.

[0030] According to still another aspect of the invention, the controlsystem may be adapted to perform self-configuration. Thus, a controlsystem may comprise a network address, which may be used topre-configure links or associations with other related control systemsin the conveyor system. For instance, each control system mayautomatically configure network links to send and/or receive informationfrom adjacent (e.g., upstream and down-stream) or related controlsystems, in order to implement one or more particular control strategiesassociated with operation of the conveyor system.

[0031] This feature facilitates ease of setup of new conveyor systems aswell as reconfiguration of existing systems, whereby manualreprogramming of individual control systems is minimized or reduced. Forexample, the control system having an address N may be configured onpower up to receive a message from a system at address N−1 to indicatethe presence (e.g., or absence) of an object in an up-stream conveyorsection. Similarly, the control system (e.g., at address N) may furtherbe automatically configured to provide a message to a down-streamconveyor section (e.g., at address N+1) indicating the presence of anobject in the current conveyor section.

[0032] To the accomplishment of the foregoing and related ends, theinvention, then, comprises the features hereinafter fully described. Thefollowing description and the annexed drawings set forth in detailcertain illustrative aspects and implementations of the invention.However, these implementations are indicative of but a few of thevarious ways in which the principles of the invention may be employed.Other aspects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a perspective view of an exemplary multi-bank conveyorsystem made up of a variety of modular conveyor sticks, the banks havingcontinuous network cables attached at one end to a central industrialcontroller;

[0034]FIG. 2 is a top plan view of an exemplary conveyor stick of FIG. 1showing its division into zones, each with a plurality of controlsystems, motors and sensors in accordance with the invention, whereinthe control systems are connected together by a shared network cablesection having connectors at upstream and downstream ends;

[0035]FIG. 3 is a side elevation view of the exemplary conveyor stick ofFIG. 2;

[0036]FIG. 4 is a detailed perspective view of the upstream end of theconveyor stick of FIGS. 2 and 3 illustrating connection of sharednetwork cable sections between connected conveyor sections to form acontinuous shared network cable;

[0037]FIG. 5 is a side elevation view of an exemplary control system inaccordance with an aspect of the invention, having a detachablecommunication port for receiving a shared network cable section andproviding control logic for an associated zone of the conveyor stick;

[0038]FIG. 6 is a figure similar to that of FIG. 3 showing analternative wiring method using a semi-continuous network cable “daisychained” along the rails of the conveyor sticks;

[0039]FIG. 7 is a schematic illustration of an exemplary control systemfor controlling a modular conveyor according to various aspects of thepresent invention;

[0040]FIG. 8 is a flow diagram schematically illustrating a method forselecting an output value for an output device or module which may beimplemented in a conveyor control system in accordance with theinvention;

[0041]FIG. 9 is a schematic diagram illustrating aspects of an exemplarylogic system for selecting an output value for an output device ormodule in a conveyor control system according to the invention;

[0042]FIG. 10 is a schematic diagram illustrating a control systemincluding the method and system for selecting an output value for anoutput device or module according to the invention;

[0043]FIG. 11 is a schematic diagram illustrating an output device ormodule in which the methods and systems of the present invention may beimplemented in a modular conveyor system;

[0044]FIG. 12 is a schematic diagram illustrating user-definedattributes in accordance with the invention;

[0045]FIG. 13 is a flow diagram illustrating an exemplary method ofproviding an output value for an output device in a conveyor controlsystem in accordance with the present invention;

[0046]FIG. 14 is a schematic diagram illustrating an exemplary outputdevice for a conveyor control system in accordance with another aspectof the invention;

[0047]FIG. 15 is a schematic diagram illustrating another exemplaryoutput device in accordance with the invention;

[0048]FIG. 16 is a schematic diagram illustrating an exemplaryconfiguration of a conveyor control system output device in accordancewith another aspect of the invention;

[0049]FIG. 17 is a schematic diagram illustrating another exemplaryconfiguration of a conveyor control system output device in accordancewith the invention;

[0050]FIG. 18 is a schematic diagram illustrating an exemplary controlsystem including an output device in accordance with the invention;

[0051]FIG. 19 is a schematic block diagram illustrating an exemplarydistributed conveyor control system in which various aspects of thepresent invention may be implemented;

[0052]FIG. 20 is a block diagram illustrating an exemplary mode changemessage in accordance with the invention;

[0053]FIG. 21 is a block diagram illustrating an exemplary step commandmessage in accordance with the invention;

[0054]FIG. 22 is a block diagram illustrating another exemplary modechange message in accordance with the invention;

[0055]FIG. 23 is a flow diagram illustrating an exemplary method ofperforming a function in a conveyor control system in accordance withthe invention;

[0056]FIG. 24 is a flow diagram illustrating further aspects of themethod of FIG. 23;

[0057]FIG. 25 is a block diagram illustrating an exemplary stepparameter message in accordance with the invention;

[0058]FIG. 26 is a block diagram illustrating another exemplary stepcommand message in accordance with the invention;

[0059]FIG. 27 is a flow diagram illustrating another exemplary method ofperforming a function in a conveyor control system in accordance withthe invention;

[0060]FIG. 28 is a flow diagram illustrating further aspects of themethod of FIG. 27; and

[0061]FIG. 29 is a flow diagram illustrating further aspects of themethod of FIGS. 27 and 28.

DETAILED DESCRIPTION OF THE INVENTION

[0062] The present invention is now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In order to provide context for the variousfeatures and aspects of the present invention, an exemplary conveyorsystem is illustrated and described. Referring now to FIG. 1, anexemplary conveyor system 10 may be assembled from a plurality ofconveyor sticks 12, each providing upwardly exposed rollers 14 formoving one or more objects 16 along a conveyor axis 18. The rollers 14of the conveyor sticks 12 may be reversible, thus allowing the object 16to be moved in either direction along axis 18 in a controlled fashion.Nevertheless, an arbitrary “upstream” end 20 and “downstream” end 22 maybe defined for each conveyor section representing one direction of flowalong axis 18 for the processes of accumulation and slug release.

[0063] The conveyor sticks 12 may be arranged in one or more parallelbanks 24 and may include alternative conveyor sticks 26 having diverterbranches 28 providing a bifurcated path splitting a single upstream bank27 into multiple downstream banks 24. The diverter conveyor sticks 26may include a movable wall (not shown), which pushes packages either tothe left or to the right. As depicted at an upstream end 20 of the banks24, a continuous network cable 30 may connect each bank 24 (e.g.,upstream ends 20 of one bank 24 to the downstream ends 22 of a next bank24) to a central programmable logic controller (e.g., PLC) 34 also asknown in the art.

[0064] The network cable 30 provides for communication of data inpackets having associated addresses identifying the destination and/orsource of the data of the packet. This addressing allows the conductorof the network cable 30 to be shared among many devices while data maynevertheless be directed to or otherwise associated with particular onesof those devices. In this regard, a destination address may be linked tothe packet indicating the device for which the data is intended.Alternatively or in combination, a source address may be attached to thepacket and the device for which it is intended may have a stored tableof addresses from which it will receive such packets. Broadcastingprotocols may also be implemented on the network cable 30. The DeviceNetstandard based on the CAN controller protocol may be suitable for thispurpose but other network protocols may be used alternatively or incombination. For example, a network cable 30 for the DeviceNet standardemploys four conductors, two for supporting data communication and twofor providing power.

[0065] Referring now to FIGS. 2 and 3, a single conveyor stick 12divides its rollers 14 into multiple zones 36. Thus, for example, aconveyor stick 12 having a length between its upstream end 20 and itsdownstream end 22 over ten feet, may include four, 2.5 foot zones 36,each with multiple rollers 14. Each zone 36 may include one motorizedroller assembly 38, for example, those having an internal motormechanism of a type well known in the art. This motorized rollerassembly 38 communicates its motion by means of belts 40 with the otherrollers 14 of the zone 36. Positioned at a downstream end of each zoneis a sensor 42 such as may receive a light beam (not shown) from anemitter (not shown), the beam crossing the upper surface of the lastroller 14 of the zone 36 at its downstream side in a directionsubstantially perpendicular to the conveyor axis 18. An object (e.g.,object 16) breaking the light beam, signals the presence of an object atthe zone.

[0066] For each zone 36, a controller card or control system 48communicates with the sensor 42 and with the motorized roller assembly38 to provide control functions as will be described. Each controlsystem 48 also communicates in shared fashion with a cable section 31.The cable section 31 runs in “daisy-chain” fashion connecting to each ofcontrol systems 48 of the conveyor stick 12, each control system 48communicating with rollers and sensors of their respective zones 36. Thediverter conveyor stick 26 of FIG. 1 may comprise a control system 48(not shown) and thus may be easily integrated into the rest of theoperation of the conveyor system 10. It will be appreciated thatalthough the exemplary control system 48 is illustrated and describedhereinafter with respect to modular conveyor systems, that the controlsystem 48 may alternatively or in combination be employed in associationwith other (e.g., non-modular or continuous) conveyor systems inaccordance with the present invention. Referring also to FIGS. 4-6, oneimplementation of the control system 48 provides for control leads 62leading to the sensor 42 and power leads 64 leading to the motorizedroller assembly 38. The control system 48 may comprise level shiftingand power circuitry for supporting the motorized roller assembly 38 andthe sensor 42. Separated power leads 65 provide power that may beswitched by the control systems 48 directly to motors of the motorizedroller assemblies 38. A connector 66 is provided to receive a networkcard 68, which attaches to the network cable and provides the necessaryprotocol for communication on the network cable 30. Other aspects of thecontrol system 48 will be illustrated and described in greater detailhereinafter. The control systems 48 may be held by side panels 50 of theconveyor stick 12 which may further serve to support the rollers 14. Theside panels 50 provide integral cable raceways 52 into which the controlsystems 48 may fit as well as the cable section 31. Cable section 31terminates in connectors 54 at its upstream and down stream endsadjacent to the upstream and downstream ends of one of the side panels50.

[0067] Referring now to FIG. 4, the side panels 50 terminate at theirupstream and downstream ends 20 and 22 at a mechanical connector 56being generally a plate perpendicular to the conveyor axis 18 andincluding two axial holes 58. The mechanical connector 56 and its axialholes 58 match with corresponding mechanical connectors 56′ and holes58′ of an adjacent conveyor stick 12′. Fasteners 60 inserted throughthese holes 58′ and 58 allow assembly of the conveyor sticks 12 togetherinto a conveyor system 10. A notch 61 in the mechanical connector 56permits passage of either cable section 31′ into the raceway 52 or cablesection 31 into the raceway 52′ where they may be attached to each othervia electrical connectors 54. A small amount of additional slack isprovided in the cable sections 31 and 31′ to permit this operation whilepreserving complete enclosure of the network cable 30 (made up of cablesections 31) within the raceway 52 or 52′. Thus, assembly of conveyorsticks 12 into a conveyor system 10 is a simple matter of joiningmechanical connectors 56′ and electrical connectors 54 of each newconveyor stick as it is added.

[0068] Referring to FIG. 5, the network card 68 may comprise an addressswitch 70 for setting a “media access layer” address of the controlsystem 48 so that data sent on the network 30 by different devices(e.g., control systems 48 and/or central controller 34) may bedistinguished. Before or at the time each conveyor stick 12 is added tothe conveyor system 10, its control systems 48 may be given a uniqueaddress via the switches 70. Alternatively or in combination, thenetwork address of the control system 48 may be programmed via messagingfrom the network 30. Where the address space (e.g., the total number ofunique addresses allowed by the network) is limited to a number lessthan the total number of control systems 48, a bridge 32 (e.g., FIG. 1)may be connected between different groupings of the conveyor sticks 12.In this manner, an expansion may be provided of the addresses that mayintercommunicate, as will be described further below.

[0069] During operation of the exemplary conveyor system 10, eachcontrol system 48 may receive data from the central controller 34. Thecontrol systems 48 may further provide data to the central controller 34upon request from the central controller 34, for example, under a simpledirector/follower protocol. The network card 68 will decode only thosemessages addressed to it according to low level procedures well known inthe art.

[0070] All pertinent data necessary for control of the conveyor stickmay be downloaded from the central controller 34 to the control systems48 including, for example, the desired motor speed and/or direction forthe motorized roller assembly 38 and delay times between actuations ofthe motorized roller assembly 38 and changes of state of the sensor 42.Commands such as for accumulation, singulation release and slug releasecan be issued from a central location or from local switches oncontrollers also attached to the network cable 30. Likewise data fromthe control system 48 may be relayed to the central controller 34including indications of jamming, the state of the sensor 42, the stateof the motorized roller assembly 38, the temperature of the motorizedroller assembly 38, current draw of the motor, etc. This information, asuploaded to central controller 34, may provide a centralized picture ofthe operation of the conveyor system 10

[0071] In addition, the central controller 34 may manage theinterconnection of the control systems 48 with its adjacent zones in itsconveyor stick 12, or in upstream or downstream conveyor sticks 12, byproviding each control system 48 with the address of other controlsystems 48 associated with its upstream and downstream zones from whichor to which sensor data may be sent. In another aspect of the invention,the control systems 48 may automatically configure themselves upon powerup to send and receive such information from one or more other adjacentor otherwise associated control systems 48, for example, based on thenetwork address setting (e.g., address switch 70). The provision of theaddress-based network 30 facilitates this self-configuration, andfurther provides for elimination of the dedicated wiring betweenconventional conveyor controllers heretofore required to implementinformation sharing between conveyor sections or zones. Further,reconfiguration of the conveyor system 10 may be easily performed from acentral location.

[0072] The logic circuitry necessary for the control system 48 toperform the various operations such as accumulation, slug release, andsingulation release, may comprise a single integrated circuit 72 in thenetwork card 68, the integrated circuit 72 also providing thecommunication protocol with the network cable 30. As used herein, logiccircuitry should be considered to embrace discrete logic devicesimplementing logical functions, programmable gate arrays and the like,and circuits such as microprocessors and microcontrollers executing astored program. In this regard, the integrated circuit 72 may handlelow-level protocols including timing, arbitration for the shared networkcable and detection of network errors and the like. As described ingreater detail hereinafter, the control system 48 may comprise a singleintegrated printed circuit board assembly having one or more of logic,I/O, communications, and power interfacing circuitry.

[0073] By investing the integrated circuit 72 with both communicationprotocol and control logic capabilities, the control system 48 may beextremely simple providing for only basic motor and sensor controlactivities while the logic of these operations is supported in theintegrated circuit 72. Nonvolatile memory within integrated circuit 72allows reconfiguration of the logic by commands from the centralcontroller 34 providing even greater configuration flexibility. Afterconfiguration by the central controller 34, much of the communication onthe network cable 30 is peer to peer between control systems 48. Thecontent of this communication may be similar to that of the prior art,however, it will be recognized that the data is communicated over theshared network cable 30, thereby reducing wiring burden in the raceways52.

[0074] In accordance with another aspect of the invention, the centralcontroller 34 may be eliminated or removed after configuration and thesystem may operate without the central controller 34 in a peer to peermode. Alternatively, a simple interface device may be attached in lieuof the central controller 34 to provide an indication of the operationof the system.

[0075] Another aspect of the invention provides for self-configurationof the control systems 48 based on a network address (e.g., as set byaddress switch 70 or via programming commands). For instance, a firstcontrol system 48 having a network address N may be adapted toautomatically configure itself to receive a message from another controlsystem 48 having address N−1, which may be located upstream of the firstcontrol system 48. In this regard, the control systems 48 maycommunicate with each other in peer-to-peer fashion in order to sharedata, for example, to implement a conveyor control strategy such assingulation, accumulation, and the like. In addition, the first controlsystem 48 may be adapted to automatically configure itself on power upto send a data message to a third control system 48 at network addressN+1, for example, to indicate the status of the conveyor zone associatedwith the first control system 48 (e.g., object present, photoswitch on,etc.). Nevertheless, such peer-to-peer communication is not necessaryand it is possible to operate the present invention in a mode in whichall sensor signals are relayed to the central controller 34 and commandsare returned to the individual control systems 48, and no logic need beincluded or programmed on the control systems 48.

[0076] Referring again to FIG. 1, multiple network cables 30 may beconnected by a bridge 32 serving a number of different functions. Thefirst function of the bridge 32 is that of mapping redundant addressspaces to different addresses so that limited address space protocolssuch as CAN may be expanded arbitrarily. Thus if addresses one through128 are used in each bank 24, the bridge 32 may concatenate a bankaddress to those addresses thereby differentiating them. Bridge 32 alsoallows interconnection of network cables 30 in situations where astraightforward daisy chaining is difficult, for example, between banks24 or branches in the case of diverter conveyor sticks 26 which providea branching topology.

[0077] Referring to FIG. 5, according to another aspect of theinvention, the control systems 48 may be given insulation displacementtype connectors 74 such as allow for connection of the control system 48to a semi-continuous ribbon cable 76. After mechanical connection of theconveyor sticks 12 into banks 24, the entire data connection of theconveyor sticks 12 may be handled by unreeling the ribbon cable alongthe raceways 52 and clamping it along its length beneath the insulationdisplacement connectors 74. Higher gauge power wiring may then be runand the connection process is complete.

[0078] Referring now to FIG. 7, an exemplary control system 48 isillustrated for controlling a modular conveyor (e.g., conveyor stick 12)having a motorized roller 38 for moving objects (e.g., object 16) on themodular conveyor and an object sensor 42 for sensing objects 16 on themodular conveyor 12. The control system 48 comprises a drive controller80 adapted to control a motorized roller 38 in the modular conveyor 12,and a communications port 82 adapted to connect the control system 48 toan address-based network 30. The communications port 82 further providesfor sending outgoing addressed data (not shown) to other devices in thenetwork 30, and for receiving incoming addressed data from the network30.

[0079] The control system 48 further comprises a logic system 84 adaptedto receive an input signal from one of the object sensor 42 via one ormore inputs 86 and the communications port 82. The logic system 84 alsoprovides a roller control signal to the motorized roller 38 via drivecontroller 80 according to the input signal. According to another aspectof the invention, the control system 48 may further comprise one or moreoutputs 88, and the logic system 84 may include an output module (notshown).

[0080] As illustrated and described in greater detail hereinafter, theoutput module may comprise a value source selector adapted to receivemessages from the address-based network 30, and a local logic functionassociated with the value source selector to create a binding, and toprovide a signal thereto. One or more outputs 88 may receive an outputvalue from the value source selector based on the signal from the locallogic function in order to provide an output signal. The value sourceselector is adapted to selectively ignore I/O and explicit messages fromthe address-based network 30 based on the binding, and to selectivelyuse an idle action and set the output value according to an idle valuewhen the local logic function is disabled. Such explicit messages maycomprise, for example, configuration information, transferred data,messages to I/O ports, component fault or status information andrequests for such, and the like, although it will be appreciated thatthe invention is not limited to any specific form of such explicitmessaging. In addition, the value source selector may selectively use afault action and set the output value according to a fault value basedon an override attribute, and selectively ignore idle messages accordingto the override attribute.

[0081] According to another aspect of the invention, the logic system 84may further comprise an indicator (not shown) adapted to receive messageinformation from the communications port 82 and providing indicatordata, as well as a logic unit receiving message information from thecommunications port 82, receiving indicator data from the indicator, andperforming a logic function. The logic unit may be adapted toselectively provide an output value to one or more of the outputs 88according to one of the message information and the logic function.

[0082] As illustrated and described in greater detail hereinafter, thelogic system 84 may be further adapted to execute a stored program andto receive a message from a master device via the communications port82, wherein the message comprises a parameter (not shown). The logicsystem 84 is further adapted to execute at least a portion of the storedprogram according to the parameter and to subsequently suspend executionof the stored program according to the parameter.

[0083] Many variations of the exemplary control system 48 may beimplemented in accordance with the present invention. For instance, thecontrol system 48 may, but need not, comprise the logic system 84,inputs 86 and outputs 88, whereby the system 48 provides for start/stopand speed control of the motorized roller 38 using the drive controller80 according to messaging from the network 30 via the communicationsport 82. In another variation, the control system 48 may comprise thelogic system 84, inputs 86, and outputs 88, whereby the system 48 mayprovide start/stop and speed control of the motorized roller 38 usingthe drive controller 80 according to messaging from the network 30 oraccording to programmable logic in the logic system 84. The inputs andoutputs 86 and 88, respectively, may thus be employed to perform controland/or interlocking functions in addition to control of the roller 38and reading of the objects sensor 42.

[0084] In another possible variation, the drive controller 80 maycomprise various forms of motor control interface, including one or morecontactors, soft starters, and variable frequency drives. This variationmay or may not include inputs 86 and outputs 88, and may operate thedrive controller according to the logic system 84 or according tomessaging from the network 30. The invention may thus comprise anynumber of combinations of local logic, communications, inputs, outputs,and drive controllers, whereby the control system 48 may beadvantageously employed in any number of conveyor control applications.In this regard, it will be appreciated that all such variations of thecontrol system 48, including those not specifically illustrated anddescribed herein, are contemplated as falling within the scope of thepresent invention.

[0085] According to another aspect of the invention, the control system48 may be adapted to advantageously select an output value source for anoutput device or module (e.g., outputs 88). This aspect of the inventionavoids the problems associated with conventional output devices byallowing a user to define one or more attributes associated with theoutput device (e.g., drive controller 80 and/or outputs 88), as well asto define a binding to local logic (e.g., within the logic system 84).Thus, a user may determine or select the output value source which willbe used by the output device under a variety of system conditions,depending on configuration of the output device or module, the currentstate of the module, and the state of a network.

[0086] Referring now to the drawings, FIG. 8 illustrates a method 102 ofselecting an output value for an output device or module (not shown)according to the invention. The method may be employed in the controlsystem 48 of FIG. 7, for example, in order to select an output value forone or both of the drive controller 80 or the outputs 88. In thisregard, the method 102 may be implemented in the logic system 84 of thecontrol system 48. As discussed in greater detail infra, a user maydefine an association (e.g., a binding) between the output device and alogic function (not shown), which may comprise, for example, locallogic. With such an association defined, the output value update beginsat step 104, after which the presence of an explicit message isdetermined at step 106. Explicit messages may be a request to change theoutput value of the module or device, for example, a configurationrequest message.

[0087] If an explicit message has been received, the message will beignored at step 108 (e.g., the value in the explicit message will not beused to set the device output value), and an object state conflict errormessage will be returned at step 110 in response to the explicitmessage. Since the receipt of explicit messages as well as I/O messagesdiscussed infra, are generally asynchronous to the updating of theoutput value, the steps 106, 108, and 110, and the processing of I/Omessages at steps 112 and 114, are done without performing the setoutput value step 138. Thus, when an output has been associated with(e.g., bound to) a logic function, it no longer allows explicitmessaging services to change its value. Instead, it will return an errorindicating an “Object State Conflict”.

[0088] Decision step 112 determines whether any I/O messages have beenreceived. If so, these are ignored at step 114, since the output deviceis associated with a logic function. As an example, an I/O message maybe sent by a PLC or other device which is running a ladder logicprogram, in order to update an output device according to the ladderlogic. When an output device is bound, it no longer uses the consumeddata from an I/O connection (e.g., with a PLC) to update its value.Instead, the source of information that it is bound to will be used.

[0089] During a normal update of the device output value, the presenceof faults is determined at step 116. When an output is bound and a“Receive Fault” event occurs or a consuming I/O connection times out,the output device may override fault action and fault value settings,based on an override attribute (not shown) at step 118. If the overrideattribute is set, the method proceeds to step 120. If not, the outputvalue is set according to a fault value at step 122. In this case, thedevice may also perform a fault action, which may comprise going to aknown output value (e.g., the fault value), or holding the last value,etc. The override attribute, fault action, and fault value may bedefined by a user via a network tool, as described in greater detailinfra.

[0090] If no faults are present, or if the override attribute is set,step 120 determines whether a force message has been received. A forcemessage may be generated by a master on a network, which tells an outputmodule to force an output to a specified state, regardless of the I/Ostate derived from a PLC logic program or from associated local logic.In some conventional systems, this is accomplished by a PLC receiving aforce message from the network, and ignoring it's own internal logic,instead sending I/O messages to an output module based on the statespecified in the force message. Thus, the output will be set to thestate specified in the force message until the module (or PLC) receivesanother message from the master.

[0091] If such a force message has been received, step 124 determineswhether the output force feature has been enabled. This feature may beimplemented via a force enable attribute (not shown). If the forcefeature is enabled, the device output value will be set according to aforce value at step 126. If no output force message is received, or ifthe force attribute is not enabled, the method proceeds to step 128,where the presence of an idle message is determined.

[0092] When an output is bound and a “Receive Idle” event occurs, theoutput may override idle action and idle value settings based on thesetting of an override attribute (not shown) at step 130, which may bethe same override attribute discussed supra with respect to faultoverride. An example of a receive idle event is where a user switches aPLC or other processor from run mode into a program mode. Where theoutput is associated with a logic function (e.g., being controlledlocally), it is assumed that the I/O connection is not needed forcontrolling the output's value, and hence the invention provides forselectively ignoring a receive idle event based on the overrideattribute. If an output is dependent on consumed data, the user canconfigure the override attribute accordingly. If the override attributeis not set, an idle action and idle value are used at step 132. The idleaction may be, for example, to hold the last valid output value, or togo to a known output value, such as the idle value. Otherwise, themethod proceeds to decision step 134.

[0093] Step 134 determines whether the logic function (e.g., locallogic) with which the output device has been associated has beendisabled. If so, the idle action and idle value are used at step 132.When an output is bound, it will enter an idle state when local logic isdisabled, during which time idle action and idle values will be applied.If the local logic is not disabled, the logic enabled output function isperformed at step 136, and the output value is set at step 138 accordingto the local logic function, after which the value source selectionmethod 102 is completed at step 140. The method illustrated in FIG. 8thus allows a user many options in selecting an output value source forthe output device or module. This provides significant advantages overconventional networked I/O where the output value is controlled byinformation received from an I/O or explicit messaging service, or inthe case of a fault or idle condition, from fault state and idle stateattributes, respectively.

[0094] Referring now to FIG. 9, a system 150 for selecting an outputvalue 152 for an output device or module 154 is illustrated, wherein theoutput device 154 comprises an output value source selector 156 fordetermining the output value 152. The system 9, moreover, may beincluded in the logic system 84 of the conveyor control system 48. Theoutput value source selector 156 receives external signals from anetwork or other communications medium (not shown), including afault/idle message 158, a force message 160, an I/O message 162, and/oran explicit message 164. The device 154 may further comprisecommunication status and network status override attributes 166 and 168,respectively. The output value source selector 156 may be bound to afunction block 170 via a binding 172. Although the exemplary system 150is illustrated with the output value source selector bound to functionblock 170, other bindings are possible, such as a binding from theoutput value source selector 156 to input 2 176. The binding 172 createsan association between the output value source selector 156 and a logicfunction 186, such as the function block 170, which may include one ormore hardware inputs 174, 176, and 178, a hardware fault input 180, I/Omessages 182, and/or explicit messages 184. In this regard, outputs maybe bound to function blocks, hardware inputs, faults, other outputs, oranything else a developer thinks may be useful in local logic 186.

[0095] Once the binding 172 has been made between the local logic 186and the output value source selector 156 of the output device 154, I/Omessages 162 and explicit message 164 will be ignored. Fault and idleconditions 158 may be selectively used or ignored based on theuser-defined settings of one or more override attributes including, forexample, communication status override attribute 166. The logic functionperformed by the function block 170 will generally provide a value forthe output 152, unless the local logic 186 is disabled. In this case thedevice 154 enters an idle state, during which time an idle action andidle values (not shown) will be applied, for example, to go to a knownvalue (e.g., the idle value), or to hold the last value.

[0096] Referring now to FIG. 10, a system 200 is illustrated, whichincludes the method and system for selecting an output value for anoutput device or module according to the present invention. Acommunications network 202 is connected between several elements of thesystem 200, including one or more computers 204 and 206, a programmablelogic controller (PLC) 208, and exemplary output modules 210 and 212.Modules 210 and 212 are illustrated as having direct access to thenetwork 202. However, it will be appreciated that the modules 210 and/or212 may alternatively be connected to a PLC or other processor via abackplane (not shown) with a communications bus (not shown) thereon,with the PLC receiving messages for the module from the network 202. Asan example, the PLC 208 may be connected to one or more I/O modules 214,216, and 218, respectively, which in turn provide outputs to, and/orreceive inputs from a process 220.

[0097] The exemplary output module 210 comprises a value source selector222 which may receive messages and/or signals from the network 202 aswell as a local logic function 224. An output 226 receives its valuefrom the value source selector 222, and provides an output to a process228. An inputs unit 230 may measure one or more process variables fromthe process 228, which may be provided thereby to the local logicfunction 224. The local logic function 224 may also be adapted toreceive and send messages via the network 202. The module 210 mayfurther comprise a processor and a stored control program (not shown)for implementing one or more control strategies to control the process228. Similarly, the module 212 includes a value source selector 240, anoutput 242, an input 244, and a local logic function 246 to providecontrol of a process 248.

[0098] According to the invention, the value source selector 222 isadapted to selectively ignore I/O and explicit messages from the network202 based on the association with the local logic function 224 (e.g.,binding), selectively use an idle action (not shown) and set the outputvalue 226 according to an idle value (not shown) when the local logicfunction 224 is disabled, selectively use a fault action (not shown) andset the output value 226 according to a fault value (not shown) based onan override attribute (not shown), and selectively ignore idle messagesfrom the network 202 according to the override attribute. The module 210of FIG. 10 thus allows a user many options in selecting an output valuesource for the output 226. This provides significant advantages overconventional networked I/O where the output value is controlled byinformation received from an I/O or explicit messaging service, or inthe case of a fault or idle condition, from fault state and idle stateattributes, respectively.

[0099] Referring now to FIG. 11, an output device or module 250 isillustrated in which the methods and systems of the present inventionmay be implemented. The module 250 comprises a processor 252 connectedwith a memory 254, and I/O section 256, and a network communicationsinterface 258. The interface 258 provides communications between theprocessor 252 and a communications network 260. In accordance with theinvention, an output of the I/O section 256 is associated with (e.g.,bound to) a logic function, which may comprise a function block, ahardware input, a fault, and/or an output. The logic function may beimplemented in the processor 252 according to a program and/oruser-defined attributes stored in the memory 254. Referring also to FIG.12, the memory 254 may contain one or more user-defined attributesassociated with an output value source selector feature of the module250. The attributes may include an idle action 270, an idle value 272, afault action 274, a fault value 276, and force enable attribute 278, andone or more override attributes 280. The processor 252 may performoutput value source selection according to the invention. Theseattributes and the various values (e.g., idle value, fault value, etc.)associated with an output device may be user-defined, for example, via acomputer or other tool sending messages across the network 260, or evenvia dipswitches on the output device.

[0100] Referring also to FIG. 8, the module 250 may compriseinstructions (not shown) in the memory 254 for implementing the outputvalue source selection method 102, by which an output value may bedetermined by the processor 252 for an output of the I/O section 256. Inthis regard, the association (e.g., binding) of an output to a logicfunction allows a user to define where the output will get its outputvalue from, based on the configuration of the module 250, the state ofthe module 250, and the state of the network 260, as discussed suprawith respect to FIGS. 8 and 9. In this regard, the processor or outputvalue source selector 252 may be adapted to selectively ignore I/O andexplicit messages from the network 260 based on the association betweenthe output and local logic, selectively use an idle action and set theoutput value according to an idle value when the local logic function isdisabled, selectively use a fault action and set the output valueaccording to a fault value based on an override attribute, andselectively ignore idle messages from the network 260 according to theoverride attribute.

[0101] Another aspect of the invention provides a method and apparatusfor providing an output value in an output device, which may be employedin the control system 48 for operation of a conveyor system 10. Thisaspect of the invention allows a user to define a logic function and toassociate the logic function with one or more status/event indicators.The logic function then provides an output value to the device outputaccording to the status/event indicators as well as the logic program.This may determine, for example, whether the output value is based on anI/O message received by the device from a network, or based on thelogic. As opposed to conventional conveyor control methods andapparatus, the present invention allows a user to define output devicebehavior in a variety of circumstances, thereby providing significantlyimproved design flexibility.

[0102]FIG. 13 illustrates a method 302 of providing an output value foran output device in a conveyor control system. An output is associatedwith a logic function at step 304 and the logic function is associatedwith one or more status/event indicators at step 306. As discussed ingreater detail hereinafter, the logic function may comprise one or morefunction blocks, for example, boolean operators, bi-stable functions(e.g., flip-flops), counters, timers, analog functions, etc. Theassociation of the logic function with the indicator at step 306 may bea logical connection (e.g., a binding) in an output module, which a usermay accomplish via a configuration tool through a network, as discussedin greater detail infra. The method also comprises receiving status andvalue messages from the network at steps 308 and 310, respectively,after which the status/event indicators are updated at step 312according to information received in the status message and furtheraccording to the status of the output device.

[0103] It will be appreciated that a single network message may includeboth value and status information. In this regard, the network messagemay include indications of the status of various network devices, forinstance, network status, devices status of other modules, etc. Themessage may also include information about the occurrence of variousevents, such as faults and the like. In this way, the method maintainssituation awareness of a variety of status/event conditions in adistributed control system, which may be taken into account indetermining an output value for the output module or device.

[0104] The status/event indicator may comprise, for example, a list ortable in control system memory, whereby a processor in the system mayupdate the information upon receipt of network message, and may accessthe information in determining an output value in accordance with theuser defined logic function. At step 314, the logic function isexecuted, wherein the associated status/event indications are consultedin determining an output value for the device. Thereafter, the logicfunction provides an output value to the output at step 316. The logicitself may compute or derive the output value, or the value may beobtained from a network value message (e.g., a typical I/O message),depending on the logic function. Since the logic function itself may beconfigured to account for one or more of the status/event indications inthe indicator, the determination of the output value according to themethod 302 provides numerous options for a user in defining the outputdevice behavior. Optionally, a network message may be sent at step 318according to the logic function and/or the indicator. For example, wherean event (e.g., a fault) causes the output value to be derived from thelogic function instead of from an I/O message, a user may wish toinitiate a network message telling other devices on the network that theoutput device is changing its control strategy because of the fault.

[0105] The method 302, thus allows significantly improved flexibility indefining or configuring distributed conveyor control system elements.The method allows the conveyor control system 48 to be aware of its ownsituation (e.g., status) as well as the status of other devices on anetwork and of the occurrence of various events in the system. Theseindications are associated (e.g., linked or bound) with a user-definedlogic function, which accounts for these indications in determining theoutput value for the device.

[0106] Referring now to FIG. 14, a system 350 and output device 352 areillustrated, wherein the device 352 is provided with a logic function354 associated with one or more status/event indicators 356, an output358, and a network interface 360. The network interface 360 transmitsand receives information to and from a network 362, in the form ofmessages. The messages may be value messages and/or status messages, orthe messages may each include both value and status information. Thestatus/event indicators 356 are likewise associated with the network,and thus may receive updated status and/or event information fromnetwork messages. The logic function 354 selectively provides an outputvalue to the output 358, which in turn provides an output signal (notshown) to a process 364 (e.g., a conveyor motorized roller). By takinginto account the status/event indicators 356, the logic function 354provides the ability to define the behavior of the output 358 in avariety of situations which was not heretofore possible.

[0107] The logic function 354 and the association thereof with thestatus/event indicators 356 in device 352 may be configured via aconfiguration tool 66 connected to the network 362. For example, a usermay define the logic function 354 in terms of various function blocks(e.g., boolean operators, flip-flops, counters, timers, etc.) and createan association between the logic function 354 and the status/eventindicators 356 using the tool 366, which may be a computer, workstation,etc. The configuration (not shown) may then be sent by the configurationtool 366 to the output device 352 via one or more messages on thenetwork 362.

[0108]FIG. 15 illustrates further aspects of the present invention,wherein an output device 400 has an output 402 for providing an outputsignal (not shown) to a process 404, such as a motorized conveyor rollerassembly. The device 400 also comprises a communications or networkinterface 406 providing for transmission and/or receipt of messages toand from a network 408. A processor 410 interfaces with the networkinterface 406 along with a memory 412 and the output 402. In addition,the device 400 may include one or more inputs 414 for measuring variousparameters or variables associated with the process 404. In this regard,the device 400 may be an I/O module, which may be integrated into orotherwise associated with the conveyor control system 48. The network408 may provide communications between the device 400 and one or moreother devices connected thereto, such as computers, workstations, otherI/O modules, PLCs, and the like (not shown), in order to form adistributed control system. It will be appreciated that the outputdevice 400 may alternatively be connected to other communicationsmediums, such as, for example a backplane communications bus, and thelike, within the scope of the invention.

[0109] In this regard, the output device 400 may receive I/O or othertypes of messages from a master (e.g., a PLC) via the network 408 (orother communications medium) and the network interface 406. Thesemessages may include value and/or status information which are used toupdate one or more status/event indicators 416 in the memory 412, and/orto provide an output value to the output 402. A user-defined logicfunction 418 may also reside in the memory 412 for determining an outputvalue for the output 402 according to one or more of the status/eventindicators 416.

[0110] According to another aspect of the invention, the logic functionmay be performed or executed by the processor 410 according to programinstructions (not shown) within the memory 412. In addition, theprocessor may update the status/event indicators 416 in the memory 412according to messages (not shown) received from other network devicesvia the network 408 and interface 406. The configuration or definitionof the logic function 418 as well as the association thereof with one ormore of the status/event indicators 416, may be performed by a user viaa configuration tool (not shown) through the network 408 and interface406. The association between the indicators 416 and the logic function418 may comprise, for example, a binding or linking, whereby the outputvalue determination takes the indicators into account. As discussed ingreater detail infra, the logic function 418 may be defined in terms ofone or more function blocks (not shown), whereby a user may configurelogical or other functions (e.g., boolean operations, flip-flops, timer,counters, and the like) in order to provide an output value (not shown)to the output 402. The logic function 418 may alternatively beimplemented be circuitry or components (not shown) other than theprocessor 410, which may be adapted to provide an output value to theoutput 402. The behavior of the output 402 may therefore be defined in avariety of event/status situations, providing the user with significantdesign flexibility not otherwise possible with conventional devices.

[0111] Referring now to FIG. 16, several aspects of the presentinvention are illustrated in which an output device 500 comprises anoutput 502 providing an output signal 504 to a process 506 (e.g.,conveyor system 10) according to an output value 508 determined by anexemplary logic function 510. The logic function 510 is illustrated ascomprising a logical function block 512 (inverter), a function 514 (A),a function 516 (B), and a function block 518 (OR), with the output ofthe OR function block 518 providing the output value 508 to the output502. It will be noted that logic function 510 may comprise functionblocks (e.g., 512, 518) as well as other functions (e.g., 514, 516).

[0112] The inputs of function block 518 are connected to the outputs offunctions 514 and 516. The inverter function block 512 and the function514, are associated with (e.g., bound to) an I/O connection healthstatus/event indicator 520 via a binding 522, with the inverter functionblock 512 providing a signal to the input of function 516. The indicator520 is one element in a status/event indicator table or list 524 whichfurther includes a message connection health indicator 526, an I/O errorindicator 528, a run/idle indicator 530, a network error indicator 532,an I/O point fault indicator 534, a hardware input indicator 536, ahardware output indicator 538, an I/O data indicator 540, and an outputdevice status indicator 542. It will be appreciated that thestatus/event indicator list 524 may comprise any number of indicatorsrelated to system and/or module status or event information, and is notlimited to those illustrated in FIG. 16.

[0113] A network interface 544 provides communication capabilitiesbetween the output device 500 and a network 546, and may be operativelyconnected to the status/event indicator list 524 as well as a messagebuffer 548. As illustrated, the output device 500 may provide an outputvalue 508 according to the logic function 510, based on one or moreentries in the status/event indicator list 524. In this way, thebehavior of the output 502 may be defined by a user, taking into accountthe status of any device in a control system, including the status 542of the output device 500. In the exemplary configuration of FIG. 16, asafety application is illustrated in which control of the output 502 isswitched between the functions A 514 and B 516 depending on the healthof an I/O connection from a master (not shown), as indicated by thestatus/event indicator 520.

[0114] If the connection is healthy, function A 514 controls the output,for example, by providing the output value 508 according to an I/Omessage (not shown) received from the network 546 via the interface 544,and provided to function A 514 of the logic function 510 from themessage buffer 548. If the I/O connection with the master is faulted,the I/O connection health indicator 520 in list 524 is updated by thenetwork interface 544, and the binding 522 between indicator 520 andlogic function 510 causes function B 516 to provide an output value 508to the output 502 via the OR function block 518.

[0115] The function B 516, for example, may implement a controlled shutdown of the process 506 due to the I/O connection health faultassociated with the master. In addition, the occurrence of such a faultmay be configured by a user to trigger transmission of a message to thenetwork 546 via the message buffer 548 and the network interface 544.This may be accomplished in the definition of the logic function 510 by,for example, linking the output of the inverter function block 512 tothe message buffer 548 as illustrated in FIG. 16. In this way, theoutput device 500 may be configured to perform a controlled shutdown ofthe process 506 according to the event status indicator 520, and tobroadcast a message across the network 546 informing one or more devicesthereon that a controlled shutdown of the process 506 is underway.

[0116] Many different configurations of functions are possible withinthe scope of the invention, including those not specifically illustratedin the drawings. In addition, many different functions are possible,including but not limited to boolean operators, flip-flops, counters,timers, analog functions, and the like.

[0117] Referring now to FIG. 17, another exemplary application of thepresent invention is illustrated wherein an output device 600 comprisesan output 602 providing an output signal 604 to a process 606 accordingto an output value 608 from a logic unit 610. The logic unit 610 isassociated with a list 624 of status/event indicators which comprises anI/O connection health indicator 620, a message connection healthindicator 626, an I/O error indicator 628, a run/idle indicator 630, anetwork error indicator 632, an I/O point fault indicator 634, ahardware input indicator 636, a hardware output indicator 638, an I/Odata indicator 640, and an output device status indicator 642. Theassociation between the event/status indicator list 624 and the logicunit 610 comprises a binding 622 which provides an input to the logicunit 610 from the I/O point fault indicator 634. The entries in thestatus/event indicator list 624 are updated by a network interface 644according to one or more messages (not shown) from a network 646, whichmay include, for example, network I/O messages, network status messages,network value messages, etc.

[0118] A message buffer 648 provides for transmission and receipt ofnetwork messages from and to the logic unit 610. Referring also to FIG.18, various aspects of the invention are illustrated in an exemplaryredundancy application. In this example, two input devices 650 and 652feed the output device 600, which provides an output signal 604 to theprocess 606 based thereon. The output device 600 may receive the values660 and 662, respectively, of the input devices 650 and 652, forexample, from the message buffer 648. This may be the case where one ormore separate input modules (not shown) on the network 646 provide thevalues 660 and/or 662. Where the output device 600 is an I/O module, theinputs may be part of the device 600.

[0119] The logic unit 610 of output device 600 compares the two inputvalues 660 and 662 before making any decisions. If one of the inputdevices 650 or 652 were to fail (e.g., device 652), the output device600 could continue to operate using only input device 650, according tothe user defined configuration of the logic unit 610. The failure of aninput in this example may be determined according to the I/O point faultindicator 634. The output device 600 can further be configured to send amessage 670 from the logic unit 610 to another device (not shown) on thenetwork 646, via buffer 648 and interface 644, to indicate that a faulthas occurred in one of the input devices 650 and/or 652.

[0120] Furthermore, the logic unit 600 could be configured to continueoperation according to one of the redundant input devices 650 or 652 fora predetermined time period after sending the message. In this case, themessage 670 could include information that an input device has failed,and the output device 600 will continue to operate according to a singleremaining input device for a specified time period. After the timeperiod has expired, the logic unit 610 may be configured, for example,to perform a controlled shut down of the process 606. The output device600 can thus notify a master controller (e.g., a PLC on the network646), via message 670, that input device 652 has failed, and thatoperation with device 650 will continue for a configurable time period.This allows, for example, time for the failed device to be replacedwithout stopping the process.

[0121] It will be appreciated that many configurations and output devicebehaviors are possible according to the invention, and that theinvention is not limited to those illustrated and described herein. Forinstance, many different logical functions may be implemented byconfiguring one or more logical function blocks with associations to oneor more status/event indicators. In this regard, the function blocks maybe boolean operators, flip-flops, counters, timers, etc., and may alsoinclude analog functions within the scope of the present invention.

[0122] Another aspect of the invention provides a system and methodologyby which a user can perform single step and/or time sliced operation ofone or more control systems 48 devices in a distributed conveyor system(e.g., system 10). The user may then perform system diagnostics, forexample, by interrogating certain control systems 48 to obtain statusinformation, output and input values, and the like. The system may thenbe further iterated and the method repeated, thus allowing theidentification of logic programming and/or hardware problems in asystem. The system and methodology of the present invention therebyprovides for significantly improved diagnostic and troubleshootingcapabilities over conventional conveyor control systems.

[0123] Referring now to FIG. 19, an exemplary distributed control system100 is illustrated in which various aspects of the present invention maybe implemented. The system 700 includes a network 702 interconnectingcomputers 704, 706, PLC 708, and control devices 710 and 712 forcommunication therebetween. The PLC 708 may be installed in a rack (notshown) along with one or more I/O modules 714A, 714B, and 714C, by whichthe PLC may communicate with the modules (hereinafter collectivelyreferred to as 714) via a bus or other communications medium (notshown). In this manner, the PLC 708 may control a process 716 via theI/O modules 714, which may or may not directly communicate with thenetwork 702.

[0124] The control devices 710 and 712 may be controllers, smart I/Omodules, and/or conveyor control systems, respectively, for controllingand/or interfacing with processes 720 and 722, respectively (e.g.,conveyor zones 36). Device 710 comprises a network interface 724providing communications between a microprocessor 726 and the network702. Microprocessor 726 is further connected to a memory 728, an inputstage 730, and an output 732. The memory 728 may store a control program(not shown) and data related to the process 720, for example, an I/Otable (not shown). The input stage 730 and the output 732 provideinterfaces between the device 710 and the process 720. Similarly, device712 comprises a network interface 734 providing communications between amicroprocessor 736 and the network 702. Microprocessor 736 is furtherconnected to a memory 738, an input stage 740, and an output 742. Theinput stage 740 and the output 742 provide interfaces between the device712 and the process 722.

[0125] In accordance with the present invention, the devices 710 and/or712 may receive a message (not shown) from the network communicationsmedium 702, wherein the message includes a parameter, execute at least aportion of the stored control program (not shown) according to themessage parameter, and subsequently suspend or stop execution of thestored program according to the parameter. The message may put thedevices 710 and/or 712 into a step mode, or may cause execution of atleast a portion of the program in the devices 710 and/or 712, which isalready in a step mode by virtue of, for example, a previous mode changemessage. The invention thus allows a user to begin execution of acontrol device program or internal logic for a limited or specified timeperiod or number of logic iterations, after which the devices 710 and/or712 will suspend execution.

[0126] Referring also to FIG. 20, an exemplary mode change message 750in accordance with the invention is illustrated having a module addressfield 752, a message type field 754, and an instruction field 756instructing the recipient control device (e.g., devices 710 and/or 712)to change mode to step mode. Following receipt of a mode change message750, the devices 710 and/or 712 may suspend execution of theirrespective stored control programs (not shown) and await another modechange message or a step command message as described in greater detailinfra. As is understood in the art, the microprocessors 726 and 736 ofdevices 710 and 712, respectively, receive messages from the network 702via the network interfaces 724 and 734, respectively.

[0127]FIG. 21 illustrates an exemplary step command message 760 inaccordance with the invention, which comprises a module address 762, amessage type field 764 indicating the type as a step command, a steptype 766, and a step parameter 768. The step type 766 may comprise, forexample, an indication of whether the desired step is a timed step or aniteration step. The corresponding step parameter 768 may comprise, forexample, a number of iterations or a step time value, depending on thestep type 766. As described in greater detail hereinafter, one or morecontrol devices (e.g., devices 710 and/or 712) may execute a portion oftheir respective stored control programs (not shown) according to thestep type 766 and the step parameter 768 upon receipt of the message 760via the network 702 or other communications medium.

[0128] Referring now to FIG. 22, another exemplary mode change message770 is illustrated having a module address field 772, a message typefield 774, and an instruction field 776 instructing the recipientcontrol device (e.g., devices 710 and/or 712) to change mode to theprevious mode. Following receipt of such a mode change message 770, thedevices 710 and/or 712 may return to execute mode and resume executionof their respective stored programs (not shown) after being in the stepmode.

[0129]FIGS. 23 and 24 illustrate an exemplary method 800 of performing afunction in a control system in accordance with the present invention.The method 800 begins at step 802 where a mode change message (e.g.,message 750 of FIG. 20) is received, after which program execution issuspended or stopped at step 804. Thereafter, the device waits for astep command message at steps 806 and 808. As will be appreciated fromthe discussion of FIGS. 27 through 29 infra, a single message maycomprise both a mode change command and a step command in accordancewith the invention. It will be further appreciated that messages otherthan step command type messages may be received at this point (e.g., I/Omessages, other mode change messages, etc.), which may be operated onand/or responded to accordingly. However, for the sake of brevity, themethod 800 is illustrated in FIG. 23 as waiting for a step commandmessage via steps 806 and 808.

[0130] Once a step command has been received, the step type andparameter are obtained therefrom at step 810. Decision step 812 thendetermines whether the step type is timed or iterations. If the steptype is timed step, the device (e.g., device 710 and/or 712) executesits stored control program according to the time specified by the steptime value parameter at step 814 before program execution is suspendedor stopped at step 816. Alternatively, if the step type is iterations atstep 812, the device executes the number of program iterations accordingto the step parameter at step 818 before program execution is stopped orsuspended at step 816.

[0131] Referring also to FIG. 24, once program execution has beenstopped or suspended at step 816, the control device waits for receiptof another message at steps 818 and 820. Once a message has beenreceived from the communications medium (e.g., network 702), the messagetype is determined at decision step 822. If the message is a stepcommand, the device obtains the step type and parameter from the messageat step 810 of FIG. 23 as discussed supra.

[0132] If the new message is not a step command or mode change typemessage (e.g., I/O or other explicit message), the device provides dataand/or status information, or otherwise responds to the message at step824, before returning to step 818 to await another message. In thisregard, data may be provided by a device such as device 710 of FIG. 19,via a message (not shown) on the network 702 to a device (e.g., computer704) which requested the data. In this manner, a user may generate stepmessages from a computer 704, and when the device 710 has completed stepmode execution and stopped, data values and/or status information may beobtained from the device 710 via I/O or other explicit messaging.Returning to FIG. 24, if the new message is a mode change message, thedevice will change mode according to the new mode change message at step826 and resume program execution according to the new mode at step 828.

[0133] In accordance with another aspect of the invention, stepparameters may be provided to a distributed control device in a separatemessage. Referring now to FIG. 25, an exemplary step parameter message900 is illustrated, having a module address 902, a message type 904indicating a step parameter message, a step type 906 indicatingiteration or timed step as described supra, and a step parameter 908corresponding with the step type 906 and indicating a number ofiterations or a step time value, respectively. This form of messageprovides step parameters to a device (e.g., device 710 and/or 712), forexample, where a prior mode change message (e.g., message 750 of FIG.20) has placed a control device (e.g., device 710 and/or 712 of FIG. 19)into step mode.

[0134] Referring also to FIG. 26, another exemplary step command message910 is illustrated having a module address 912 and a step commandmessage type 914. This message may be used to initiate a step of adevice in accordance with the invention, where, for example, the devicehas been provided with a step type 906 and a step parameter 908 via aprevious step parameter message 900 such as that illustrated in FIG. 25and described supra. Many different message protocols are possible,including those not specifically illustrated in the figures, which fallwithin the scope of the present invention.

[0135] Referring now to FIGS. 27-29, another exemplary method 1000 ofperforming a function in a control system or device is illustrated inaccordance with the invention. A change mode message is received at step1002, after which execution of the program stored in the control deviceis stopped or suspended at step 1004. Thereafter the device waits for astep parameter message at steps 1006 and 1008. It will be furtherappreciated that messages other than step parameter type messages may bereceived at this point (e.g., I/O messages, other mode change messages,etc.), which may be operated on and/or responded to accordingly.However, for the sake of brevity, the method 1000 is illustrated in FIG.27 as waiting for a step parameter type message via steps 1006 and 1008.

[0136] Once a step parameter message (e.g. message 900 of FIG. 25) isreceived at step 1008, the step type and parameter are obtainedtherefrom at step 1010. The device then waits for receipt of anothermessage at steps 1012 and 1014 (FIG. 28).

[0137] Upon receipt of a message at step 1014, decision step 1016determines the message type. If the message is a step command message,the step command is executed as described in greater detail infra andillustrated in FIG. 29. If the message is a change mode message, thedevice changes mode according to the mode change message at step 1020,after which program execution is resumed according to the new mode atstep 1022. If the new message is not a step command or mode change typemessage (e.g., I/O or other explicit message), the device (e.g., device710 and/or 712) provides status information and/or data (e.g., via anetwork message to the requester), or otherwise responds to the messageat step 1024, and returns to step 1012 to await further messages.

[0138] Referring now to FIG. 29, if the message received at step 1014 isa step command type message, the device determines whether the step type(e.g., step type 906 of FIG. 25) is timed or iteration at step 430. Ifthe step type is timed step, the device (e.g., device 710 and/or 712)executes its stored control program according to the time specified bythe step time value parameter at step 1032 before program execution issuspended or stopped at step 1034. Alternatively, if the step type isiterations at step 1030, the device executes the number of programiterations according to the step parameter at step 1036 before programexecution is stopped or suspended at step 1034. Once the program hasbeen stepped (e.g., timed step via step 1032 or iteration stepped viastep 1036), and the program execution has again been stopped orsuspended at step 1034, the device again waits for a message at step1012 of FIG. 28. Thus, a user may perform stepped execution of thecontrol or logic program stored in the device, and obtain process orother information from the device at step 1024 via I/O or other explicitmessages while the program execution is suspended. Proceeding in thisfashion, a user may advantageously troubleshoot system programming andother errors in widely distributed control systems.

[0139] It will be recognized that more than one device (e.g., devices710 and/or 712) may be placed into step mode and respond to stepcommands, etc., via a single message. In this way, a user cansynchronize single steps of distributed control system execution with asingle network message. For example, a user may send a message fromcomputer 704 in FIG. 19 to PLC 708, device 710 and device 712 to performa specified time period of execution of the programs stored therein.Thereafter, data relating to the controlled processes 716, 720, and/or722, respectively, can be obtained from the devices 708, 710, and/or 712while the execution of these programs is stopped or suspended. Thismethod or process can be repeated any number of times in order tofacilitate the identification of problems and/or programming errors inthe system hardware, logic programs, actuators, etc. In addition,different devices (e.g., devices 708, 710, and/or 712) may be sentdifferent step parameters via a number of addressed step parametermessages, and then started via a single broadcast step command message.The present invention thus provides powerful diagnostic and debuggingmethods particularly applicable to widely distributed control systems.It will be further recognized that many message protocols are possiblewithin the scope of the invention, beyond those illustrated anddescribed herein.

[0140] Although the invention has been shown and described with respectto certain illustrated aspects, it will be appreciated that equivalentalterations and modifications will occur to others skilled in the artupon the reading and understanding of this specification and the annexeddrawings. In particular regard to the various functions performed by theabove described components (assemblies, devices, circuits, systems,etc.), the terms (including a reference to a “means”) used to describesuch components are intended to correspond, unless otherwise indicated,to any component which performs the specified function of the describedcomponent (i.e., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure, which performs thefunction in the herein illustrated exemplary aspects of the invention.In this regard, it will also be recognized that the invention includes asystem as well as a computer-readable medium having computer-executableinstructions for performing the steps of the various methods of theinvention.

[0141] In addition, while a particular feature of the invention may havebeen disclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. Furthermore, to the extent that the terms“includes”, “including”, “has”, “having”, and variants thereof are usedin either the detailed description or the claims, these terms areintended to be inclusive in a manner similar to the term “comprising.”

What is claimed is:
 1. A control system for a modular conveyor having amotorized roller for moving objects on the modular conveyor and anobject sensor for sensing objects on the modular conveyor, the controlsystem comprising: a drive controller adapted to control a motorizedroller in the modular conveyor; a communications port adapted to connectthe control system to an address-based network, to send outgoingaddressed data to other devices in the address-based network, and toreceive incoming addressed data from the address-based network; and alogic system adapted to receive an input signal from one of the objectsensor and the communications port, and to provide a roller controlsignal to the motorized roller according to the input signal.